Gehlenite

Formula : Ca2(Al2Si)O7

Family: 
Melilite
Space group: 
Tetragonal - Scalenohedral H-M Symbol (4 2m) Space Group: P 421m
Dana class: 
55.4.1.2 (55)Sorosilicate Si2O7 Groups, Generally with No Additional Anions (55.4) with cations in [8] and lower coordination (55.4.1) Melilite group
High temperature: 
High temperature mineral from around 780C to 1600C
Geological context: 
Contact metamorphic mineral in limestone. Skarns along the contact of a diorite intrusion . Mineral also found in metallurgical slags and incineration byproducts from municipal solid waste (bottom ash, fly ash).

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
274.200 90.150 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. -3786276 (Ref.: Internal calculation) -3985000 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. 210.100 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. 206.40 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
227.25 89.00 -42.12 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
Reaction properties

Gehlenite + 10H+ ⇌ 2Al+3 + 2Ca+2 + H4SiO4 + 3H2O

298.15 K, 1 bar log10K: 55.24 ΔH°r:-494151 J·mol-1 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp.
T(°C) 0 25 60 100 150 200 250 300
log10K 63.10 55.24 46.09 37.66 29.21 22.32 16.39 11.02
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-1883.292415 -0.291570 126206.925765 673.957321 -5822490.611233